Abstract:

Soil erosion is a serious problem in South Africa and correct veld management is therefore
very important for the preservation of plant and animal communities, to preserve the soil, as well as to maintain a sustainable tourist attraction. The Ben Lavin Nature Reserve, south of Louis Trichardt, has a problem with the invasion of sicklebush (Dichrostachys cinerea), that takes over and wipes out the natural vegetation communities and reduce the soil quality. It was considered necessary to conduct a soil analysis in the area, since the application and efficacy of chemical herbicides is greatly dependent on the clay content of the soil, which can be determined during a textural analysis. The objective of this study, therefore, was to conduct an analysis of the soil types iii the reserve according to certain physical and selected chemical parameters. By comparing certain parameters with one another, a holistic view of the soils in the area was obtained, as well as the identification of areas with unique soil qualities. A method to reach optimum veld conditions and to reduce soil erosion by wiping out the sicklebush invaders, was also
suggested. A total of 240 soil samples were collected by means of augering along six representative routes in the reserve. The samples were analised during the field work, followed by subsequent laboratory analyses, computer analyses, a cartographic phase and a GIS-phase. It was determined that the soils in the reserve are generally very weakly developed (5 - 25cm in depth), and also relatively immature, with sub-angularly rounded particles dominating. The maturity increases with soil development, which shows that chemical weathering is the main soil forming prdbess in the area, and that the soils are formed in situ. The median (central particle size), as well as the average particle size, fall mostly in the course soil particle size class (0,5 - 1mm diameter), which indicate a high permeability, porosity and infiltration, and low water retention capacity and subsequent low run-off in the area. The soils are generally slightly acidic (pH 5 - 6). The low silt and clay content, generally between one and five percent, with a maximum of 12,9 %, means that the potential fertility is low and small amounts of plant nutrients are released. The relatively low pH (not too acidic), and low silt and clay content, prove that chemical weathering is taking place at a very slow rate. This can probably be attributed to the relatively low rainfall in the area. Carbonates are absent or occur in very limited quantities in the area, but can be observed where chemical weathering has exposed calcretes and released carbonates. The fact that the soil maturity also increases as the
grading of the soil particles improves, supports the fact that the soils in the reserve were
formed in situ, and do not consist of transported material. Fluvial erosion thus did not play a role in soil formation the area.